1. Field of Invention
The present invention relates to the optimized email transmission, and particularly to a method for pushing email in heterogeneous networks as well as a mobile terminal and a mail-pushing server utilizing the method.
2. Description of Prior Art
With the advancement of mobile communication technology, a mobile terminal is currently equipped with multiple network interfaces and thus the capability of simultaneously accessing several kinds of networks, such as Bluetooth, WIFI and GPRS. Although the data transmission rate is high in the mode of WIFI, for a mobile device, the operating distance is limited and the standby power consumption is rather large. Consequently, the mobile device in such mode cannot live up to the service requirements of long-term standby for mobile mail and waiting for new mail notification. For example, with WIFI function enabled, HP iPaq can be on standby for only 2 to 3 hours before it runs out of the power. In addition, the standby status can last less than 24 hours for the WIFI mobile phone from CISCO. On the other hand, the technologies such as GPRS, EVDO and 3G provide a long-distance network access capability and give better solutions for the standby annoyance to a mobile device. Due to the limitation on frequency bandwidth and terminal performance, however, the data transmission rate is relatively low, in particular, far lower than that achievable by a WIFI-enabled device.
In order to overcome the standby problem with the WIFI-enabled device, some solutions have been proposed, such as Power-Save Extension Protocol by Wi-Fi Multimedia and APSD (Automative Power-Save Delivery) by Atheros. All of these schemes require that wireless access points and terminals be modified to support more complex power-saving management protocols, for the purpose of a better power-saving effect. Moreover, even if these protocols are added, the standby duration for WIFI can be extended from several hours to less than 20 hours, which lags far behind the requirements of 7*24 hours corporate mail service.
Currently, various corporate email-pushing schemes are all implemented over WAN (Wide Area Network) such as GPRS/CDMA. Therefore, it is difficult to make full use of the characteristics of heterogeneous networks in selecting a cheap and rapid WIFI for network access, even with the wide popularity of WIFI access environment. Meanwhile, a proprietary WIFI mail client end suffers from certain power management strategy, leading to a scheme of short standby duration and poor applicability.